In driving devices, also called drivers, metal strip is clamped between a pair of rollers and driven or deflected. Drivers are typically used in rolling trains, where they are arranged upstream of rolled-strip coilers in order to set the strip tension upstream of the coiler by means of two rolls, namely the driving roller and the supporting driving roller. Directional drivers have the additional object of reducing lateral creeping of the rolled strip prior to coiling. To this end, for example the pivotable driving roller is actuated in such a way and is adjusted toward the stationary supporting driving roller that, on account of the position of the driving roller with respect to the supporting driving roller, the rolled strip undergoes a desired strip tension and a desired lateral displacement.
Such directional drivers are known for example from EP747147B1 or AT500689B1.
EP747147B1 shows a directional driver, the pivotable driving roller of which is arranged mounted between two rockers by means of the two ends of the driving roller axle. The two rockers are connected rigidly to a torsion spring of a frame which forms a rotary axle for the rockers.
AT500689B1 discloses a similar directional driver, in which, however, the rockers can be pivoted independently of one another on a rotary axle of a frame.
The driving roller and the supporting driving roller of a directional driver have to be cleaned and polished regularly, since, for example on account of carbon caking, particles of dirt present on the strip to be coiled, or surface defects in the strip to be coiled which are caused during the initial pass, the surface of the driving roller and of the supporting roller become uneven, and this can lead in turn to damage to the surface of the strip to be coiled.
In EP747147B1 or AT500689B1, the driving roller axle is mounted on a bearing region of the rockers, with the driving roller being located in each case underneath the rocker. The bearings of the driving roller are, in order to avoid damage during the push of the initial pass, are set in a play-free manner for example by spring-activated balancing.
It is not possible to remove the driving roller upward, since the rocker is in the way of such a removal and blocks the upward path. For removal downward, to the right or to the left, in the operating state the path is blocked by the supporting driving roller and the frame. Before removal becomes possible, therefore a blocked path has first to be opened.
In order to make it possible to clean and polish the driving roller and the supporting driving roller, normally the pair of rockers on which the driving roller is mounted is pivoted by means of rocker cylinders into an intermediate position; this is likewise necessary for exchanging the driving roller. The intermediate position is often reached after the pair of rockers has been pivoted through 180°. Subsequently, the driving roller and the supporting driving roller are usually cleaned and sanded or polished by hand in the installed state. There is a safety risk on account of cleaning and sanding or polishing in the plant. This is because the persons dealing with these processes have to position themselves within the plant between the plant parts, which thus have to be reliably shut down and blocked. In addition, there is a safety risk on account of the time pressure for carrying out these tasks, since cleaning and sanding or polishing have to be carried out in the time period of 10 to 15 minutes required for changing the working rolls of frameworks. If cleaning, sanding and polishing does not produce a sufficiently uniform surface on the driving roller or supporting driving roller, or in the event of damage, the driving roller or the supporting driving roller has to be removed from the frame, following pivoting of the rockers, and exchanged for a new driving roller or supporting driving roller. To this end, in the case of directional drivers according to EP747147B1 or AT500689B1, the entire rocker structure, including the driving roller, has to be uninstalled. On account of the multiplicity of connecting elements to be released and the mass of the frame including the driving roller, maintenance of driving rollers and supporting driving rollers causes a significant and time-consuming amount of work. Furthermore, it is not easy to access the driving roller for maintenance work when it is arranged between the rockers.